1. Field of the Invention
The present invention relates to an oral composition, in particular an oral composition with improved cosmetic, sensory, protective and therapeutic benefits for the oral cavity.
2. The Related Art
More particularly, it relates to an oral care composition which contains an encapsulated agent, capable of exerting a cosmetic, sensory, protective or therapeutic benefit in the oral cavity.
Dentifrice compositions comprising encapsulated materials are already known in the art. For example, JP 55 100 309 (Lion) discloses a dentifrice composition comprising microcapsules comprising silicone oil which is a foam-depressing agent. The capsules according to this invention have an average particle size ranging from 5 to 50 .mu.m. The capsules are designed so as to be crushed and thereby release the silicone oil only after a recommended period of brushing has elapsed. In this way the anti-foam effect of the silicone oil provides a sensorial indication to the user that a suitable period of brushing has elapsed.
The disadvantages with such small microcapsules are that they are less likely to get trapped by the tip end of the toothbrush and are, therefore, less likely to be ruptured during brushing, so that the microcapsules remaining unbroken are liable to cause lowering of the sense of pleasant feeling. They may also be too small to provide any visual aesthetic effect to the consumer. Furthermore, they may get trapped in the interdental spaces.
GB 1 381 444 (Blendax-Werke) discloses a highly speckled toothpaste comprising microcapsules having a transparent shell material encapsulating a solution or suspension of colouring matter in a physiologically inert solvent. An especially preferred physiologically inert solvent is paraffin oil and the capsules have an average particle size ranging from 100 to 900 .mu.m. The capsules described are designed to crush immediately during use, which implies that their contents, i.e. the colouring matter and the paraffin oil, are also released immediately. This causes an immediate foam depression, as paraffin oil is a known foam depressing agent.
EP-A-0 711 544 (Kao) discloses a dentifrice composition comprising capsules containing agar as a main component of a coating forming substance. The capsules have an average diameter of from 0.3 to 3 mm.
However, agar is an unstable material in the presence of anionic surfactants, e.g. alkali metal alkyl sulphate surfactants, such as sodium lauryl sulphate, which is a conventional material commonly used in dentifrice compositions, and these capsules, made from agar as coating forming material suffer from leaching in such dentifrice compositions.